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Cleaning and Shaping of the Root
Canal System
Dr János Vág Phd
Department of Conservative Dentistry
Semmelweis University
Based on Mahmoud Torabinejad, Richard E. Walton, ENDODONTICS: PRINCIPLES AND PRACTICE 4th edition
PRINCIPLES OF CLEANING AND
SHAPING TECHNIQUES
• The criteria of canal preparation include
– developing a continuously tapered tunnel
– maintaining the original shape of the canal
– maintaining the apical foramen in its original
position
– keeping the apical opening as small as possible
(prevention of reinfection, apical stop for
obturation)
– developing glassy smooth walls
Untouchables
Procedural Errors
• loss of working length:
– Inadequate reference point
– Apical block
– Ledge formation
• apical transportation zipping → apical perforation
• stripping perforations
• Instrument fracture
Reasons of procedural errors:
Restoring force (stiffnes) in curved canal (Standard technique – stainless
steel file)
Ledge formation – loss of
working length
apical transportation zipping → apical perforation
Reasons of procedural errors:
Stripping perforation due to asymmetrical over prepartion
Perforation
Right position
Reasons of procedural Errors • Torsional or cyclic fatigue of the file → Instrument fracture
• Prevention:
– Minimal force on file
– Straight-line access
– Inspection of the file
– Rotary: • cyclicl axial motion
• file manufacturer recommends: – speed (in revolutions per minute [rpm])
– torque control
• Preflaring the canal (crown-down)
• Clean the file regularly
• Single use?
Preparation technique
– Step-Back Technique
– Step-Down Technique
• Crown-down Technique
– Anticurvature Filing
– Balanced Force Technique
– Nickel-Titanium Rotary Preparation
– Final Apical Enlargement and Apical Clearing
– Recapitulation
– Combination Technique
Movements for preparations
• Watch winding
(clockwise/counterclockwise
rotation, reciprocating)
• Reaming (clockwise cutting
rotation)
• Filing (scraping), Circumferential
filing
Watch-winding
Standardized technique • Aim: standardized uniform tapered canal
Standardized
diameter ISO
Standardized
conicity ISO 1 mm
0.27 mm
MAF: 0.25 mm
ISO file
1. Watch-winding (reamer, K-files)
2. all instruments introduced into a root
canal to the entire working length,
gradually larger and larger
3. MAF = the size of the last file used
4. Filling: single-cone technique
5. Cons: curved canals will be wider than
the last used instrument, exacerbated by
the pulling portion of the hand
movement. Adequate compaction of
guttapercha in such small a taper (0.02)
is difficult or impossible.
0.02
Standardized
diameter ISO
canal 1 mm
0.30 mm
MF: 0.25 mm
ISO file 1. Filing (+apical last mm: rotation)
2. Incrementally reducing the working
length when using larger and stiffer
instruments
3. More tapering: Avoid procedural
error, easier rinsing, compactable
filling, better copying the non-
rounded cross-section
4. Cons: procedural error still occur,
apical dentin plug
0.05
Step-back technique • Aim: increase the diameter without procedural
error
Standardized
diameter ISO
canal 1 mm
0.30 mm
MF: 0.25 mm
ISO file 1. Rotation motion (watchwinding or
reaming)
2. Gradually move deeper with
smaller file
3. More tappered canal: less error,
easier rinse, compactable filling ,
less dentin plug
4. Cons: in narrow canal ledge
formation may occur
0.05?
Step-down technique • Aim: the most infected coronal debris is removed
first
Standardized
diameter ISO
canal 1 mm
1. Nowadays: preferable with engine
driven instrument with rotary
movement
2. The determination of the WL done
after the coronal preparation
0.04, 0.05, 0.06, 0.07,
0.08, …..
• Aim: even more aggressive coronal flaring to avoid intrusion of the debris and better
determination of the apical size
Crown-down technique
(modification of the step-down technique)
An example of crown-down technique
Coronal flare (orifice
shaper)
Apical shaping
WL determination
Aim: To reduce procedural error significantly in case of K-file
This technique keeps the file centrally in the canal
Balanced-force technique
Passive introduction
Light apical pressure
sufficient apical pressure to keep the file in constant length
Advance of the instrument apically
File removing for cleaning
• Length control
• Speed control
• Torque control
Endodontic Intracanal Lubricants
Nickel Titanium versus stainless steel files
NiTi
• Shape memory
• High flexibility
• Cyclic and torsional
fatigue
• Expensive
Stainless Steel
• Recording curves
• Rigidity
• More resistant to
fatigue
• Cheap
Hand versus engine driven rotary
instruments • NiTi rotary instruments:
– Less debris and irritants enter the periapical tissue (Madhusudhana et al. Contemp Clin
Dent. 2010 Oct-Dec; 1(4): 234–236.), causing less inflammation and complaints (Siqueira
Int Endod J. 2003 Jul;36(7):453), except the reciproc ( Bürklein and Schäfer, J Endod.
2012 Jun;38(6):850-2. )
– Less preparation error (Esposito and Cunningham CJ. J Endod 1995;21:173-176.,
Sonntag et al. Int Endod J 2003;36:715-723.)
– Convenient
– Faster:
• Very narrow canal
• Standardized, smooth, equally tapered canal is easier to fill in
• Hand instruments:
– Better adapt to the individual canal morphology
– Elliptic, figure-8 cross-section
– Big curvature: precurved stainless steel hand file
– Less file separation?
Nickel-Titanium Rotary Preparation
• Crown down techniques, – preflaring,
deeper and deeper, smaller and smaller • Profile, Protaper
• Standardized technique – reaming movement, – whole working length
larger and larger file • MTWO, Ligth Speed
• Balanced force-technique – One file endo
• Wave-One, Reciproc
MTWO system
Tapering of the guttapercha points should match the
canal morphology after preparation
Reciproc system
0.33-0.25 = 0.08
Reciproc system